Journal of Geosciences, 52 (2007), 199–210

DOI: 10.3190/jgeosci.013

Original paper

Supergene uranium mineralization from Horní Halže near Měděnec
(Krušné hory Mountains), Czech RepublicJiří Sejkora1*, Jiří Čejka1, Vladimír Šrein2
Department of Mineralogy and Petrology, National Museum, Václavské nám. 68, 115 79 Prague 1, Czech Republic;
jiri_sejkora@nm.cz
2Institute of Rock Structure and Mechanics, Academy of Sciences of the Czech Republic, V Holešovičkách 41, 182 09 Prague 8,
Czech Republic*
Corresponding author
1

Supergene uranium mineralization was studied at Horní Halže near Měděnec, Krušné hory Mountains, Czech Republicwith the help of optical and electron scanning microscopy, X-ray powder diffraction and chemical analyses. The uranyl
minerals kasolite, metatorbernite, phosphuranylite, šreinite, uranophane and uranosphaerite, together with goethite andbismutoferrite, were observed and described in detail. Chemical composition and unit-cell parameters of the minerals studied are given and compared with published data. Possible paragenetic sequences and conditions of origin are
discussed.
Keywords: uranyl, supergene minerals, uranium, unit-cell parameters, chemical composition, Horní Halže, Czech Republic
Received: 11 October 2007; accepted 11 December 2007; handling editor: E. Jelínek

1. Introduction
Research on physico-chemical and paragenetic propertiesof minerals containing hexavalent uranium in the form of
uranyl ion, UO22+, focuses in principle in two directions.
The first is the classic basic research, in which so far
unknown information about uranyl minerals is obtained,
inclusive their paragenesis, origin, formation and occurrence at individual localities. The second direction
is concerned with the possibilities of contamination by
pollutants released during weathering of natural accumulations of primary uranium minerals at shallow levelsof the Earth’s crust. This research potentially yields
fundamental information for solution of the long-term
storage of spent nuclear fuel. For this purpose are studied
products of long-term weathering of natural uraninite andother U4+-bearing mineral phases directly in the geological environment exposed to actions of exogenic factors(Finch and Ewing 1992; Wronkiewicz and Buck 1999;
Shoesmith 2000; Čejka 2002 and references therein).

2. Occurrence
The surroundings of Horní Halže (2 km WSW of Měděnec,Krušné Hory Mts., Czech Republic) are located in thecentral part of the Kovářov-Halže Fold. The complicatedstratigraphic and tectonic position is characterised by alternating bands of garnet mica schists, two-mica schists,migmatites and muscovite orthogneisses. In the flat-lying
structures, a recurrence of allochthonous bodies of carbonate rocks, and especially barren as well as magnetitebearing skarns, may be observed. The faults in this region
are marked by dykes of Tertiary basalts and intrusions ofVariscan spherulitic granite and quartz porphyry. A seriesof low-temperature quartz and hematite-quartz veins at
Horní Halže, Kamenné, Mýtinka and other localities havebeen occasionally exploited as a source of decorationstone, such as zoned amethyst–chalcedony, jasper, andagate (Šrein et al. 2000).
In this region, there is a group of occurrences of radioactive mineralization, which has been a subject to an
intensive exploration activity, especially in fifties andsixties of the 20th century (Šrein et al. 1996). However, nolocality has reached importance of an industrial deposit
and only some ore was exploited during the exploration.
The most important occurrence of uranium mineralizationin this region, apart from the mine No. 62 Přísečnice, are
the NNW–SSE trending veins, explored by undergroundworks starting from the Měděnec mine. They were represented by quartz–carbonate (with dolomite predominance) gangue. In the vein filling, products of arsenide,sulphoarsenide and sulphide stage prevail over productsof the uraninite stage (Šrein 1978). The occurrences ofuranium “blacks” in quartz veins have been investigatednear Kamenná (south of Mědenec); fluorite, sphalerite,
galena and pyrite were found in the association (Šrein
et al. 1996).
www.jgeosci.org

Jiří Sejkora, Jiří Čejka, Vladimír Šrein

Fig. 1 Topographic situation of the Horní Halže uranium occurrence.

The studied samples were collected at agrarian heapsof stone at the margin of the downhill run localized approximately 500 m south of the church in the village ofHorní Halže (Fig. 1). In these stone heaps, both barren andmagnetite skarns were observed besides quartz gangue,
fragments of mica schists, migmatites, and gneisses.
In the nearest surroundings of the studied locality,
occurrences of uranium mineralization were discovered
in Dolní Halže village. Here exploration by the Uranium
Enterprise (Zafirov and Surazhskii 1960) verified a radiometric anomaly at the intersection of a quartz veinwith transversal E–W fault, which coincided with amacroscopic appearance of a uranyl silicate. In addition,
200

in the dump material after medieval mining of iron ore
north of Horní Halže, an occurrence of probable torbernite was found.

3. Methods applied in the study
Macro- and microscopic character of the studied mineralphases was observed in incident light using an optical
microscope Nikon SMZ 1500. This microscope wasalso utilized for handpicking of monomineralic phases
for further study. Surface morphology was studied byan electron scanning microscope Tesla BS 340 (Czech

Supergene uranium mineralization from Horní Halže

Geological Survey, Prague) and Jeol JSM-6380 (Facultyof Science, Charles University, Prague) on gold-coatedsamples.
The X-ray powder diffraction patterns of the studied
mineral phases were obtained using the powder diffractometer HZG4-AREM/Seifert (step-scanning, CuKα
radiation, 50 kV/40 mA). To minimize the complicatedshape of the background due to classic glass sample
holder, the studied samples were placed on the surface ofa flat silicon wafer from alcoholic suspension. The positions and the intensities of the reflections were calculatedusing the Pearson VII profile shape function by ZDS
program package (Ondruš 1995). The measured patterns
were indexed by the data calculated from the publishedcrystal structure informations (Lazy Pulverix program– Yvon et al. 1977). Unit-cell parameters (all in 10-10 m)
were refined by the program of Burnham (1962).
The studied samples have been analyzed semiquantitatively by an energy dispersive microanalyzer Link
ISIS at an electron scanning microscope CamScan 4(Faculty of Science, Charles University, Prague) at acceleration voltage 20 kV, a sample current 2.5 nA and 2µm electron beam diameter. A natural unpolished sample
surface has been utilized. Quantitative chemical analyses
were carried out by means of a Cameca SX 100 electron microprobe in wavelength dispersive mode (Joint
Laboratory of Electron Microscopy and Microanalysis of
Masaryk University and Czech Geological Survey, Brno,
performed by R. Škoda and J. Sejkora). The machine
has been operated at an acceleration voltage 15 kV, asample current 4 nA, and an electron beam diameter of
2–3 µm (2 nA and 20 μm in the case of metatorbernite).
The following lines and standards were employed: Kα:
Ca and Fe (andradite), S (barite), Mg (olivine), K, Si andAl (sanidine), Na (albite), Zn (ZnO), P (fluorapatite); Lα:
Cu (dioptase), As (InAs); Lβ: Ba (barite); Mα: Pb (vanadinite); Mβ: U (U), Bi (Bi). Peak counting times were
20 s for main elements and 60 s for minor elements. The
counting time for each background was 1/2 of the peaktime. Raw intensities were converted to the concentrations using automatic PAP (Pouchou and Pichoir 1985)
matrix correction software package.

dium-grained (2–3 mm) quartz, small irregular quartz
crystals 0.5–2.0 mm are present, but quartz aggregateswith a distinct pitted surface due to leaching are moreabundant. No additional primary mineral phases wereobserved. The studied samples show a low or moderatelevel of radioactivity.

4.1. Bismutoferrite, BiFe3+2(SiO4)2(OH)Bismutoferrite forms yellow (with a shade to green andbrown) very thin earthy coatings characterized by rugged surface. It is deposited on goethite in cavities andespecially in small fissures of quartz gangue. Coatings
are formed by very small (several µm), imperfect tabular
crystals. Bismutoferrite forms coatings on an area of a few
mm2 in maximum. Because of its very limited amounts,
it was not possible to verify its presence by X-ray diffraction. During the study of its chemical composition,
substantial contents of Bi, Fe and Si were proved, with aminor admixture of Al. This information agrees with theideal formula of bismutoferrite, BiFe2(SiO4)2(OH).

4.2. Goethite, α-Fe3+O(OH)
Goethite was found as a prevailing phase filling cavities
in the central part of the studied quartz gangue, where
it forms coatings up to 1 mm thick, with hemisphericalsurface (Fig. 2). The aggregates consist of idiomorphic
crystals only 2–4 µm in size. The observed goethite ismacroscopically black-brown to black, earthy to massive with dull to earthy lustre. Goethite is the oldest
supergene mineral phase in the studied association, onto
which crystals of uranosphaerite and other mineral phases
were deposited.

4. Descriptions of minerals and theirstructural and chemical properties
All samples studied originally formed parts of a single
irregular, partly rounded block with cavities up to 5×2×2
cm, and with a rim of quartz gangue, approximately
25 cm in diameter. No other occurrences of radioactive
mineralization were found in the surroundings, in spiteof the intesive efforts and use of a sensitive radiometer.
In addition to the fine-grained (0.1–0.2 mm) and me-

Fig. 2 Hemispherical aggregates of goethite formed by tiny crystals(2–3 µm across) with idiomorphic uranosphaerite crystals on their surface, Horní Halže near Měděnec, SEM photo A. Gabašová, J. Sejkora(Tesla BS 340).

201

Jiří Sejkora, Jiří Čejka, Vladimír Šrein

Tab. 1 Unit-cell parameters of goethite (for orthorhombic space group Pnma)
locality
Horní Halže
synthetic
Gelnicareference
this paper
Hazemann et al. (1992)
Sejkora et al. (2001)a9.969(4)9.955
9.946(3)b3.024(1)
3.023
3.018(1)The X-ray powder data of the goethite sample studiedagree very well with the reference data of the PDF 2
Database and the theoretical pattern calculated from thecrystal structure of goethite (Hazemann et al. 1992). The
refined unit-cell parameters also agree well with otherpublished parameters for this mineral species (Tab. 1).
Only the majority content of Fe was inferred from thechemical analysis of goethite from Horní Halže. Verylow, minor contents of Al, U and sporadically Bi (approximately below 0.1 wt. %) were found.

c4.616(2)4.616
4.611(1)V
139.2(1)
138.9
138.41(6)indicate a significant Pb deficiency: only 0.71–0.81 apfu
in comparison with the ideal formula. This deficiency
is balanced by notable K substitution in this structural
position (0.09–0.14 apfu), besides minor contents of Bi,
Ca, Fe, Ba and Zn. We have found no similar publishedinformation on potassium content in the structure ofkasolite. On the basis of Si+P+As = 1, the empirical formula of kasolite from Horní Halže may be expressed asfollows: (Pb0.75K0.12Bi0.02Ca0.01Fe0.01Ba0.01Zn0.01)Σ0.93(UO2)1.05[(SiO4)0.95(PO4)0.05]Σ1.00 . H2O.

4.3.	Kasolite, Pb(UO2)(SiO4). H2O
In cavities of quartz gangue, kasolite forms very abundant, lightly to brightly yellow hemispherical aggregatesup to 1 mm in size, formed by tiny tabular crystals. Individual, very fragile, thin tabular crystals (20–100 µm
across) are intergrown to fan-shaped aggregates (Fig. 3).
Kasolite was also observed together with uranophane
as a part of isolated, yellow earthy pseudomorphs after
primary uraninite (spherical aggregates with a diameter
up to 3 mm) in quartz gangue. It also occurs as yellow
to yellowish–white thin coatings up to 5×20 mm in fissures of quartz gangue. Kasolite is often intergrown withuranophane in these aggregates.
The X-ray powder data of kasolite from Horní Halže
agree well with those calculated from crystal structure by
Rosenzweig and Ryan (1977) in positions of individual
diffraction maxima; substantial differences were observed
between the measured and calculated intensities. Thisis probably caused by the preferred orientation of the(h00) type. A similar phenomenon was observed for kasolite from Jánská žíla in Příbram (Škácha and Sejkora
2001). The refined unit-cell parameters of kasolite from
Horní Halže (Tab. 2) are similar to those published forthis mineral from Jáchymov (Ondruš et al. 1997). Other
authors presented insignificantly lower dimensions of theunit cell. The quantitative analyses of kasolite (Tab. 3)

Fig. 3 Fan-shaped aggregates (up to 50 µm) formed by thin tabular crystals of kasolite, Horní Halže near Měděnec, SEM photo A. Gabašová,J. Sejkora (Tesla BS 340).

4.4. Metatorbernite, Cu(UO2)2(PO4)2.8 H2OMetatorbernite was observed in cavities of quartz gangue
as individual, bright green, transparent to translucent,tabular and rarely also bipyramidal crystals up to 1 mm
long; there were also observed their intergrowths up to
3 mm across and sporadically also imperfectly developed
leaf-shaped crystals up to 8–9 mm in length. The formation of metatorbernite in cavities of quartz gangue tempo-

Tab. 2 Unit-cell parameters of kasolite (for monoclinic space group P21/c)
locality
Horní Halže
JáchymovPříbram
Shinkolobwe
KatangaRýžoviště

202

reference
this paper
Ondruš et al. (1997)Škácha and Sejkora (2001)
Rosenzweig and Ryan (1977)
Huynen et al. (1963)
Sejkora et al. (1994)a6.738(2)6.730(6)6.707(1)6.704(2)6.660
6.709(4)b
6.977(2)7.022(7)6.950(2)6.932(2)6.960
6.932(4)c13.271(4)13.307(9)13.258(4)13.252(7)13.23013.240(7)β104.28(3)104.90(1)104.20(2)
104.2
104.0
104.15(4)V
604.6(4)607.7
599.1(3)597
595.0
597.1(6)Supergene uranium mineralization from Horní Halže

Tab. 3 Chemical composition of kasolite from Horní Halže (in wt. %)
K 2O
CaO
FeO
BaO
PbO
ZnO
Bi2O3
SiO2
As2O5
P2O5
UO3
H2O*

mean
0.96
0.12
0.14
0.16
28.78
0.12
0.65
9.76
0.08
0.61
51.77
3.10

total

96.25

range (4 analyses)
0.71 – 1.13
0.00 – 0.27
0.03 – 0.27
0.00 – 0.40
27.21 – 31.24
0.00 – 0.31
0.47 – 0.76
9.53 – 10.03
0.00 – 0.22
0.31 – 0.82
49.99 – 52.57

The H2O* contents were calculated on the basis of theoretical content
H2O = 1 in kasolite formula

rally overlapped with that of kasolite and uranosphaerite.
However, in some places this mineral is distinctly older
or younger. In fissures of quartz gangue, metatorbernite
forms imperfect tables grouped into coatings on a surface
up to 5×10 mm and belongs here to the youngest mineralphases.
The X-ray powder pattern of metatorbernite from
Horní Halže agrees very well with the reference data of
the PDF 2 Database and also with the theoretical data
calculated from the crystal structure analysis data of thesynthetic metatorbernite (Locock and Burns 2003). The
measured pattern indicates a distinct preferred orientationof the (h00) type in the sample, caused by a perfect cleavage. The refined unit-cell parameters (Tab. 4) indicate aslightly increased As content in the uranyl anion sheet
in metatorbernite from Horní Halže (Fig. 4). This is inagreement with its chemical analysis (Tab. 5). Phosphorus contents in tetrahedral site vary between 1.46 and1.59 apfu and are accompanied by As content in the range
0.41–0.54 apfu. The following empirical formula wasFig. 4 Binary plot of unit-cell parameters a vs. c for minerals of themetatorbernite–metazeunerite series (published data are given in
Tab. 4).
Tab. 5 Chemical composition of metatorbernite from Horní Halže
(in wt. %)
Na2O
K2O
CaO
FeO
PbO
CuO
ZnO
Bi2O3
As2O5
P2O5
UO3
H2O*

mean
0.05
0.09
0.14
0.07
0.31
8.16
0.11
0.15
5.67
11.48
62.52
15.21

total

103.97

range (3 analyses)
0.00 – 0.15
0.02 – 0.18
0.10 – 0.21
0.00 – 0.13
0.00 – 0.52
7.97 – 8.42
0.08 – 0.14
0.05 – 0.24
4.86 – 6.48
10.78 – 11.89
62.28 – 62.84

The H2O* contents were calculated on the basis of theoretical content
H2O = 8 in metatorbernite formula

Tab. 4 Unit-cell parameters of metatorbernite (for tetragonal space group P4/n)
mineralmetatorbernite
metatorbernite
metatorbernite
metatorbernite
metatorbernite
metatorbernite
metatorbernite
metazeunerite
metazeunerite
metazeunerite
metazeunerite
metazeunerite

locality
Horní Halže
synt.
Schneeberg
Vathi, GreeceRýžoviště
Jáchymov
Jáchymovsynt.
Majuba Hill
Cínovec
Jáchymovreference
this paper
Locock and Burns (2003)
Ross et al. (1964)
Stergiou et al. (1993)
Sejkora et al. (1994)
Ondruš et al. (1997)
Ondruš et al. (1997)
Locock and Burns (2003)
Ross et al. (1964)
Walenta (1965)
Jansa et al. (1998)
Ondruš et al. (1997)

P>As
P
P
P
P
P
P
As
As
As
As>P
As

a
6.9907(8)6.9756(5)6.969(1)6.972(1)
6.9533(8)6.978(3)6.982(1)7.1094(1)
7.12
7.104
7.080(2)
7.113(1)c17.353(2)17.349(2)17.306(5)17.277(8)17.283(3)17.37(1)17.356(5)17.416(1)
17.45
17.45
17.394(5)17.433(3)V
848.1(1)844.2(1)
840.5
839.8
835.6
845.8
846.1
880.3(1)
884.6
880.6
871.9
882.0

203

Jiří Sejkora, Jiří Čejka, Vladimír Šrein

calculated from the average of three point analyses on
the basis of (P + As) = 2: (Cu0.97K0.02Na0.02Ca0.02Pb0.01Zn0.01
Fe0.01)Σ1.06(UO2)2.07[(PO4)1.53(AsO4)0.47]Σ2.00 . 8.00H2O.

4.5. Phosphuranylite,
KCa(H3O)3(UO2)7O4(PO4)4 . 8 H2O
Phosphuranylite forms bright yellow, in places up to­orange coloured, distinctly crystalline coatings on an area
up to 5×5 mm. The coatings are seen as intergrowth ofthin tabular crystals (Fig. 5) having the size 10–30 µm.
The individual crystals are yellowish, transparent, withan intense vitreous to adamantine lustre. Phosphuranylite
does not show any fluorescence in short- or longwave
UV radiation. Uranosphaerite, metatorbernite, kasolite
and uranophane were observed in close association withphosphuranylite.
The measured X-ray powder data of phosphuranylite
from Horní Halže (Tab. 6) agree with experimental data
given for this mineral in the record 39-1350 of the PDF 2
Database with an exception of a distinct preferred orientation of the (h00) type. However, the data also agree withthose given for yingjiangite, that may be identical withphosphuranylite and probably also isotypic dewindtite.

Fig. 5 Rich aggregates formed by thin platy phosphuranylite crystals,
Horní Halže near Měděnec, SEM photo J. Sejkora (Jeol JSM-6380),
width of figure 45 μm.

The refined unit-cell parameters of phosphuranylite from
Horní Halže (Tab. 7) agree with the data published forthis mineral, however, they are also comparable with theunit-cell parameters for its Pb-analogue dewindtite, and,of course, also with yingjiangite. Phosphuranylite can be
distinguished from dewindtite on the basis of comparisonof their unit-cell parameters b
and c (Fig. 6).
Tab. 6 X-ray powder diffraction pattern of phosphuranylite from Horní Halže
Demartin et al. (1991)
h
k
l
dobs.
I/Io
dcalc.
hkldobs.
I/Io dcalc.
studied the X-ray single crys1
1010.4164
10.345
7
1
1
2.200
4
2.200
tal structure of phosphura0
0
2
8.706
8
8.647
0
0
8
2.163
5
2.162
nylite and proposed for this
2
0
0
7.873
100 7.867
2
0
8
2.083
5
2.085
mineral an ideal formula
3
1
1
4.717
5
4.714
6
4
0
2.084
KCa(H 3O) 3(UO 2) 7O 4(PO 4) 4 .
0
2
3
4.417
5
4.415
2
6
3
2.054
3
2.053
8 H 2O. For yingjiangite – a
1
3
0
4.398
3
4.394
6
2
5
2.000
4
1.999
mineral probably identical with
3
1
2
4.264
4
4.263
8
0
0
1.96616
1.9667
phosphuranylite – an ideal for4
0
0
3.934
57
3.933
7
3
2
1.9647mula K2Ca(UO2)7(PO4)4(OH)6 .
2
3
3
3.858
8
3.850
0
6
5
1.90863
1.9084
6 H2O was inferred (Zhangru
2
0
4
3.790
5
3.790
8
2
1
1.87937
1.8765
etal. 1990), and for probably
0
4
0
3.436
5
3.432
2
6
5
1.854031.8546
isotypic
dewindtite the for4
2
1
3.347
9
3.348
0
4
8
1.82863
1.8293
mula
Pb
[H(UO
) O (PO4)2]2 .
2
4
0
3.146
7
3.146
2
2
9
1.801922.8013
3
2 3 2
12
H
O
(Piretetal.
1990). The
0
2
5
3.090
8
3.089
8
0
4
1.791831.7902
2
above given ideal formulae in5
1
0
3.068
6
3.067
0
0
10 1.7298
4
1.7295
dicate that the chemical com5
1
1
3.022
4
3.020
4
6
5
1.71623
1.7170position of minerals related
4
3
3
2.931
5
2.937
2
0
10 1.6899
2
1.6891
2
2
5
2.876
8
2.875
6
4
6
1.6887and close to phosphuranylite
6
0
0
2.620
4
2.622
2
8
0
1.67713
1.6768has not been unambiguously
6
0
2
2.507
4
2.509
8
0
6
1.62602
1.6246solved as yet (Sejkora et al.
3
1
6
2.479
5
2.484
1
3
10 1.6098
3
1.60932003). Moreover, Demartin et
4
4
2
2.478
8
4
4
1.58793
1.5873al. (1991) presented in their
4
2
5
2.427
6
2.429
0
4
10 1.5431
3
1.5445
formula of phosphuranylite
6
2
1
2.425
10 2
1
1.52754
1.5276
oxonium ions, H3O+. The pres6
0
4
2.242
3
2.242
10 0
4
1.47734
1.4785ence of H 3O + was supposed
4
4
4
2.220
3
2.219
4
8
4
1.4782using bond-valence parameter
X-ray powder diffractometer HZG4-AREM/Seifert, step-scanning 0.05o/6 s in the range 7o–66o 2θ CuKα. calculations, however, such
204

Supergene uranium mineralization from Horní Halže

Tab. 7 Unit cell parameters of phosphouranylite and related minerals
mineralphosphuranylite
phosphuranylite
phosphuranylite
phosphuranylite
phosphuranylite
phosphuranylite
phosphuranylite
phosphuranylite
phosphuranylite
phosphuranylite
phosphuranylite
phosphuranylite
phosphuranylite
phosphuranylite
phosphuranylite
phosphuranylite
yingjangite
dewindtite
dewindtite
dewindtite
dewindtite
dewindtite
dewindtite
dewindtite

occurrence
Horní Halže
Sardinia
Bois NoirPeveragno
ZambiaMargnac–Rýžoviště
KladskáJáchymovPředbořice
KladskáChotěboř
Horní Slavkov–
Urgeirica
TongbiguanRýžoviště
Shinkolobwe
Grury
KasoloJáchymov
Jáchymov
Katangareference
this paper
Demartin et al. (1991)
Demartin et al. (1991)
Demartin et al. (1991)
Demartin et al. (1991)
Piret and Piret-Meunier (1991)Šaškin and Sidorenko (1975)
Sejkora et al. (1994)
Pauliš et al. (1999)
Ondruš et al. (1997)
Sejkora (1993)
Sejkora (1993)
Sejkora (1993)
Plášil et al. (2006)
PDF 6-43
Hoggart and Nuffield (1954)
Zhangru et al. (1990)
Sejkora et al. (2003)
Piret et al. (1990)
PDF 39-1350
Hogarth and Nuffield (1954)
Ondruš et al. (1997)
Ondruš et al. (1997)
PDF 8-328a15.734(2)15.899(2)15.778(3)15.890(6)15.862(6)15.835(7)15.95(2)15.780(7)15.82
15.48(2)15.85(1)15.83(2)15.772(4)15.774(4)15.85
15.85(1)15.99(1)15.725(2)16.031(6)15.826(6)16.00
15.817(8)15.79(3)16.01

b13.729(4)13.740(2)13.769(2)13.790(5)13.702(5)13.724(4)13.75(2)13.725(8)13.73
13.82(2)13.70(1)13.70(1)13.734(4)13.791(3)13.74
13.76(1)13.73(2)13.629(3)13.605(2)13.641(2)13.66
13.667(5)13.62(1)13.70

c17.295(4)17.300(3)17.330(3)17.322(5)17.253(7)17.324(6)17.38)4)
17.307(8)17.34
17.41(4)17.31(1)17.27(2)17.291(5)17.318(4)17.42
17.42((1)
17.33(1)
17.317(3)17.264(6)17.299(7)17.62
17.286(6)17.32(1)17.50

V3736(1)
3779
3765
3796
3750
3765
3812
3748(2)
3766
3725
3759
3745
3745
3767.53794
3799
3804(5)3711(1)
3765
3735
3851
3737
3725
3838

All published data are transformed into position of orthorhombic space group Cmcm.

calculations are not given in the cited paper by Demartinand co-workers. The presence of H3O+ ions was proved
neither in the single crystal structure analysis by Piretet al. (1990), nor in the study of the infrared spectrumof phosphuranylite (Čejka 1999). Quantitative chemical
analysis of phosphuranylite from Horní Halže (Tab. 8)
Tab. 8 Chemical composition of phosphuranylite from Horní Halže
(in wt. %)Fig. 6 Binary plot of unit-cell parameters b vs. c for phosphuranylite,
yingjangite and dewindtite (previously published data are given in
Tab. 7).

K 2O
CaO
FeO
BaO
MgO
PbO
CuO
ZnO
Al2O3
Bi2O3
SiO2
As2O5
P2O5
SO3
UO3
H2O*

mean
1.90
2.02
0.04
0.42
0.08
3.24
0.16
0.09
0.03
0.81
0.21
0.17
10.26
0.05
73.87
7.20

total

100.53

range (5 analyses)
1.58 – 2.02
1.84 – 2.18
0.00 – 0.10
0.24 – 0.50
0.00 – 0.18
2.74 – 3.77
0.00 – 0.42
0.00 – 0.28
0.00 – 0.06
0.39 – 1.31
0.18 – 0.26
0.02 – 0.35
10.08 – 10.49
0.00 – 0.13
72.50 – 75.39

The H 2O* contents were calculated from the formula KCa(H3O) 3(UO2)7(PO4)4O4 . 8 H2O respecting the corresponding charge balance205Jiří Sejkora, Jiří Čejka, Vladimír Šrein

Tab. 9 Unit-cell parameter of šreinite and asselbornite
mineralšreinite
asselbornite
asselbornite
asselbornite

occurrence
Horní Halže
Schneeberg
Schneeberg
Schneeberga15.5728(7)15.66
15.6568(3)15.613(1)reference
Sejkora and Čejka (2007)
Sarp et al. (1983)
Sarp et al. (1983)*
Sejkora and Čejka (2007)

V3776.6(5)3840.43838.0(2)3805.9(7)* unit-cell parameter refined by Sejkora and Čejka (2007) from X-ray powder pattern published by Sarp et al. (1983)

enables to conclude that the studied mineral contains,apart from K and Ca, additional cations, of which themost important is Pb (0.33–0.46 apfu). In the tetrahedral
position, besides the dominant P (3.76–3.90 apfu), Si (upto 0.11), As (up to 0.08), and S (up to 0.04 apfu) are alsopresent. If the formula proposed for phosphuranylite by
Demartin et al. (1991) is used, chemical composition of
the mineral from Horní Halže (average of 5 point analyses) may be expressed on the basis of (P + As + Si + S)
= 4 by the following empirical formula: K1.07(Ca0.96Pb0.39
Bi0.09Ba0.07Mg0.05Cu0.05Zn0.03Al0.02)Σ1.68(H3O)1.77(UO2)6.88O4[(PO4)3.85(SiO4)0.09(AsO4)0.04(SO4)0.02]Σ4.00 . 8.00H2O.

4.6. Šreinite, Pb(UO2)4(BiO)3[(PO4]2(OH)7 .
4 H 2O
It was observed as irregular yellow coatings with adistinct orange tint, up to 0.2 mm thick, having rugged
glossy surface (area up to 2×3 mm) in fissures of quartz
gangue. It is lighter than the coexisting coatings andcrystals of uranosphaerite, which they overgrow. Šreinite
shows vitreous to subadamantine lustre, it is semi-opaqueand translucent only in thin fragments, isotropic in transmitted light, with high refractive indices. No fluorescenceat 254 and 366 nm of ultraviolet light was observed.
This mineral was first considered on the basis of X-ray
powder pattern and semiquantitative chemical analyses as(PO4)-rich asselbornite. Asselbornite is in general a veryrare mineral species. Up to now it was found on a few
samples from Schneeberg, Saxony, Germany (Sarp et al.
1983; Martin and Massanek 1995) and from Tirpersdorf,
Vogtland, Germany (Witzke 1996). The following detailed mineralogical study proved that the natural phasefrom Horní Halže is unambiguously a new mineral species. This new mineral and its name were approved by

IMA Commission on New Minerals and Mineral Names.
Detailed description of this new mineral species, together
with new data for analogous asselbornite, are given by
Sejkora and Čejka (2007).
Šreinite is cubic, possible space group Im3m, I432,
Im3 or I23. Its fully indexed X-ray powder diffraction
pattern is given by Sejkora and Čejka (2007). The refined unit-cell parameter is compared in Tab. 9 with thedata for asselbornite published by Sarp et al. (1983) andby Sejkora and Čejka (2007). According to Sejkora andČejka (2007) average chemical composition of šreinite is
BaO 0.08, CaO 0.18, MgO 0.01, PbO 7.78, Bi2O3 29.73,
SiO2 0.18, P2O5 3.41, As2O5 3.79, UO3 49.23, H2Ocalc.
(5.68), total (100.07) wt. %. It may be expressed on thebasis of 2 atoms in tetrahedral site (P+As+Si) by thefollowing empirical formula: (Pb0.83Ca0.08Ba0.01Mg0.01)Σ0.93(UO2)4.10(BiO)3.04 [(PO4)1.15(AsO4)0.78(SiO4)0.07]Σ2.00(OH)7.02.4 H2O.

4.7. Uranophane, Ca(UO2)2(SiO3OH)2.5 H2OUranophane was found in fissures of quartz gangue as
coatings on a surface up to 5×10 mm, where this mineralis intergrown with kasolite. It also forms coatings withgreyish-brown shade (not typical of the mineral). It wassporadically observed as aggregates formed by needleshaped crystals up to 5–10 µm long. As a rule, uranophane with kasolite forms a part of rare yellow powderedpseudomorphs after primary uraninite.
The X-ray powder pattern of uranophane from HorníHalže is in good agreement with the reference data fromthe PDF 2 Database and theoretical data calculated
from the crystal structure information of this mineral (Ginderow 1988). The refined unit-cell parameters(Tab. 10) compare well with the range of published pa-

Tab. 10 Unit-cell parameters of uranophane (for monoclinic space group P21)
locality
Horní Halže
Bois Noirs
JáchymovRýžoviště
––206

reference
this paper
Ginderow (1988)
Ondruš et al. (1997)
Sejkora et al. (1994)
Stohl and Smith (1981)
Barinova et al. (2001)a15.943(6)15.909(6)15.909(6)15.968(9)15.86(1)15.92(2)b
7.028(5)7.002(3)7.007(4)7.024(3)6.985(7)6.985(3)c6.671(3)6.665(3)6.669(2)6.680(3)6.641(5)6.670(4)β97.23(5)97.3
97.447(5)97.12(5)97.55(3)97.3

V741.5(5)
736.5
737.2
743.4
729.2
735.7

Supergene uranium mineralization from Horní Halže

rameters for natural uranophane samples. Quantitative
chemical study of uranophane from Halže (average fromtwo point analyses): CaO 6.59, BaO 0.13, PbO 0.44,
Bi2O3 0.24, SiO2 12.89, As2O5 0.34, P2O5 1.18, UO3 70.74,
H2Ocalc. (12.48), total (105.03) wt. % leads on the basis of(2 Si + As + P) to the empirical formula: (Ca1.00Pb0.02Ba0.01
Bi 0.01) Σ1.04(UO 2) 2.11[(SiO 3OH) 1.83(PO 4) 0.14(AsO 4) 0.03] Σ2.00 .
5H2O. Elevated PO4 contents (0.11–0.18 apfu) should be
mentioned, because such high values have not been given
for uranophane yet.

4.8. Uranosphaerite, Bi(UO2)O2OH
Uranosphaerite may be related in the studied association
to the relatively abundant minerals. It occurs here in twomorphological types. The first is bound to cavities in thecentral part of the quartz vein, where it forms simple andwell formed crystals having the size of 5–10 µm and pervasive subparallel intergrowths up to 0.05–0.5 mm in size
(Figs 7 and 8). Crystalline aggregates up to 3 mm acrosswere rarely observed. The morphology of crystals is consistent with monoclinic symmetry, crystal faces are often
rugged and curved. Uranosphaerite crystals have darkorange to yellowish-brown colours and intense vitreous

Fig. 7 Subparallel intergrowths of uranosphaerite crystals, Horní Halže
near Měděnec, SEM photo J. Sejkora (Jeol JSM-6380), width of figure
160 μm.

Fig. 8 Group of uranosphaerite crystals, Horní Halže near Měděnec,SEM photo J. Sejkora (Jeol JSM-6380), width of figure 350 μm.

lustre. In cavities of quartz gangue, they grew on older
goethite and are accompanied by light yellow kasolite
and green metatorbernite. The second type is represented
by the occurrence of uranosphaerite in the form of darkorange coatings in fissures of the quartz gangue. The surface of coatings is formed by small (up to 10 µm) crystals
with parallel orientation. Coatings of uranosphaerite form
areas up to 3×5 mm and are overgrown by light orange
coatings of younger šreinite. Other mineral phases in fissures (kasolite, dewindtite, uranophane, metatorbernite)
are distinctly younger and partly spatially separated fromthe couple uranosphaerite – šreinite.
The crystals of uranosphaerite from Horní Halže werestudied with single crystal X-ray methods (Hughes et al.
2003). The primitive monoclinic cell was found, but the
crystal structure could not be solved due to poor qualityof crystals. Fully indexed X-ray powder diffraction pattern of uranosphaerite from Horní Halže together witha description of its additional characteristics (especiallyvibrational characteristics) are given in the paper by Sej­
kora et al. (in print). Unit-cell parameters are comparedwith other published data in Tab. 11. According to Sejkora
et al. (l.c.), the empirical formula Bi1.02(UO2)0.99O2.02(OH)may be inferred from the average chemical compositionof studied uranosphaerite – Bi2O3 44.75, UO3 53.54, H2O(1.71), total (100.00) wt. %.

Tab. 11 Unit-cell parameters of uranosphaerite (for monoclinic space group P21/n)
locality
Horní Halže
Clara mine, D
synthetic
synthetic

reference
Sejkora et al. (in print)
Hughes et al. (2003)
Hughes et al. (2003)
Protas (1959)a7.558(1)7.559(2)7.540(3)7.65(4)b
7.824(1)7.811(2)7.801(3)7.78(4)c7.699(1)7.693(2)7.674(3)7.53(4)β92.90(1)92.88(3)92.948(7)93(1)

V454.7(1)453.6(2)450.75(1)448207Jiří Sejkora, Jiří Čejka, Vladimír Šrein

5. Comments on the origin of supergene
uranium mineralization at Horní Halže
near Měděnec
The primary mineralization of the Horní Halže occurrence was probably represented by bismuth, arsenides
or rather native arsenic, pyrite and uraninite or uranium
blacks in quartz gangue, which does not contain any
carbonates. In comparison with the so called five-element association (known in the near surroundings, e.g.
at Měděnec), the absolute deficiency in Ag, Co and Ni is
characteristic of Horní Halže. Other elements present in
the studied association, i.e. Ca, P and Si, were derived
from altered wall rocks. The Pb contents in kasolite andšreinite are most probably of radiogenic origin withregard to the fact that no other Pb oxidic minerals were
found at this locality.
The studied mineral association has been formed byintense weathering at conditions of an in situ supergenezone. Rich accumulations of limonite, formed by weathering of hematite and partly magnetite, associated withskarns and hematite–quartz veins, were mined in the past
locally (Šrein et al. 1996). On the basis of the presence ofindividual mineral species and their spatial development,
one can attempt to infer the character of the supergene
process. It involved distinctly oxidizing conditions, neutral or slightly acidic pH (low mobility of Bi ions) andsolutions of the uranylarsenate/uranylphosphate typewith a moderate predominance of (PO4) over (AsO4). It
is proposed that during the evolution of the studied association, the transfer of released components reachedthe maximum distance of several cm.
The supergene mineral association in the central
porous part of the quartz gangue may be expressed asfollows: quartz – goethite – uranosphaerite, kasolite,
and metatorbernite. In the fissures of quartz gangue
there are local older coatings of uranosphaerite andšreinite, younger aggregates of kasolite, uranophane
and the youngest metatorbernite. Some changes in pH
and component concentrations may be expected duringformation of the individual mineral species (Langmuir
1978; Chernikov 1981; Finch and Murakami 1999). The
uranyl mineral paragenetic sequence may be therefore
interpreted as follows: uranosphaerite (very low solubility, pH approximately 2.5) – kasolite, uranophane (pHapproximately 4.5–5.0, lower solubility of kasolite thanthat of uranophane) – phosphuranylite, šreinite, metatorbernite (pH approximately 7.5–8.5, respecting thedifferent solubility of the mentioned mineral species).
Acknowledgements The authors would like to thank the
Ministry of Culture of the Czech Republic, which has
financially supported this work as a part of the project
MK00002327201 and Grant Agency of the Academy of208

Sciences of the Czech Republic (project A3407401). The
authors express their thank also to the late A. Gabašová(Czech Geological Survey, Prague, Czech Republic) for
her help with the semiquantitative analysis of the chemical composition of the studied mineral samples and SEM
photos, and to U. Kolitsch (Universität Wien, Austria)
with R. Škoda (Masaryk University, Brno) for their help
in laboratory treatment of studied material.

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209Jiří Sejkora, Jiří Čejka, Vladimír Šrein

Supergenní uranová mineralizace z Horní Halže u Měděnce (Krušné hory), Česká republika
Supergenní uranová mineralizace z výskytu Horní Halže u Měděnce (Krušné hory) byla studována za využití optické a elektronové
scanovací mikroskopie, rentgenové práškové difrakce a chemickým analýz na elektronovém mikroanalyzátoru. Zjištěny zde byly minerály uranylu – fosfuranylit, kasolit, metatorbernit, šreinit, uranofán a uranosférit, které jsou spolu s goethitem a bismutoferritem v práci
podrobně popsány. Chemické složení a mřížkové parametry pro jednotlivé zjištěné minerální druhy jsou porovnány s publikovanými
daty. Dále jsou v práci diskutovány i pravděpodobné paragenetické sekvence a podmínky této minerální asociace.

210